1885 380 sl starves for gas over an idle fuel presure at pump 85 psi

Hi
this will most likely be a prob with the iac [idle air control] this is mounted on the throttle body which is where the air filter hose connects. If you have the resources to scan the ecm you can retrieve codes this would really help I finding the problem.

After re reading your post I see the problem is above idle. This could be a fuel filter problem, or a injection pump malfuntion.
It seems the fuel pressure is there at the rail but seems a little high to me. Possibly a fuel pressure regulator isat fault.